Interactions between Geogrid Interactions between Geogrid and Sand with/without Tire and Sand with/without Tire Chips Including Sensitivity Chips Including Sensitivity Analyses and SimulationsAnalyses and Simulations

Khurram ShehzadKhurram Shehzad

st104789st104789

14 May 200814 May 2008

Geotechnical and Geoenvironmental Engineering

ContentsContents

1.1. IntroductionIntroduction

2.2. ObjectivesObjectives

3.3. Scope of WorkScope of Work

4.4. Methodology and Laboratory TestMethodology and Laboratory Test

5.5. Numerical SimulationsNumerical Simulations

6.6. Sensitivity AnalysesSensitivity Analyses

7.7. ConclusionsConclusions

IntroductionIntroduction

When earth structures are constructed on When earth structures are constructed on soft clay deposit following problems are soft clay deposit following problems are occurred;occurred;

Large vertical settlementsLarge vertical settlements

Lateral deformationsLateral deformations

IntroductionIntroduction

Solution of the problems;Solution of the problems;

Mechanically Stabilized Earth (MSE) Mechanically Stabilized Earth (MSE) StructureStructure

Lightweight backfill materialsLightweight backfill materials

Objectives Objectives

To determine the index properties of To determine the index properties of Ayutthaya sand and tire chips-sand Ayutthaya sand and tire chips-sand mixture. mixture.

To determine the To determine the Shear strength parameters Shear strength parameters Interaction coefficientsInteraction coefficients Efficiency of geogridEfficiency of geogrid

ObjectivesObjectives

To simulate the pullout and direct shear To simulate the pullout and direct shear tests results using FE software PLAXIS 2Dtests results using FE software PLAXIS 2D

Sensitivity analyses of the important Sensitivity analyses of the important parameters affecting the pullout testparameters affecting the pullout test

Scope of WorkScope of Work

Laboratory TestsLaboratory Tests

Numerical SimulationsNumerical Simulations

Materials for this StudyMaterials for this Study

1.1.AyutthayaAyutthaya sandsand

2.2.Tire chips-sand mixtureTire chips-sand mixture

3.3.Polyfelt geogridPolyfelt geogrid

Basic Concepts of MSEBasic Concepts of MSE

Fill material

Reinforcing material

Facingmaterial

Soil/ReinforcementSoil/Reinforcement InteractionInteraction

Soil or rigid block

A= PulloutA= Pullout ResistanceResistance

B=Direct Shear ResistanceB=Direct Shear Resistance

Laboratory TestsLaboratory Tests

Direct Shear TestsDirect Shear Tests

Pullout TestsPullout Tests

Large Scale Direct Shear TestsLarge Scale Direct Shear Tests

Large Scale Direct Shear TestsLarge Scale Direct Shear Tests

Longitudinal section

Cross section

Large Direct Shear Apparatus

Large Scale Direct Shear TestsLarge Scale Direct Shear TestsDirect shear failure envelopes of the sand and tire chips-sand mixture without geogrid

0

20

40

60

80

100

0 20 40 60 80 100 120 140

Normal pressure (kPa)

Max

imu

m d

irec

t s

he

ar s

tres

s (k

Pa)

0

20

40

60

80

100

120

140

0 20 40 60 80 100 120 140

Sand only Tire chips-sand mix

Supawiwat (2002) Prempramote (2005)

Shehzad (2008) Shehzad (2008)

Sand only Tire chips-sand mixture

Large Scale Direct Shear TestsLarge Scale Direct Shear TestsDirect shear failure envelopes of the sand and tire chips-sand mixture with geogrid

0

20

40

60

80

100

120

0 20 40 60 80 100 120 140

Normal pressure (kPa)

Max

imu

m d

irec

t s

he

ar s

tres

s (k

Pa)

0

20

40

60

80

100

120

140

0 20 40 60 80 100 120 140

Tire chip-sand mix Sand

Prempramote (2005) Shehzad (2008)

Series6 Series7

Shehzad (2008)

Tire chips-sand mix Sand only

(Polyfelt geogird) (Polyfelt geogird)

(Polyfelt geogird)

Pullout TestsPullout Tests

Pullout TestsPullout Tests

Longitudinal section

Cross section

Pullout Apparatus

Pullout TestsPullout Tests

0

20

40

60

80

100

120

0 20 40 60 80 100 120 140

Normal stress (kPa)

Ma

xim

um

pu

llo

ut

res

ista

nc

e (

kN

/m)

Sand Only Tire Chip-Sand Mix

Supawiwat (2002) Prempramote (2005)

Series7 Series8

Shehzad (2008) Shehzad (2008)

Sand only Tire chips-sand mix

Slippage failure

Breakage failure

(Hexagonal grid)

(Geogrid) (Geogrid)

(Geogrid)

Maximum pullout resistance versus normal stress for sand and tire chips-sand mixture

Interaction CoefficientsInteraction CoefficientsDirect shear interaction coefficients between backfill materials and geogrid

Interaction CoefficientsInteraction CoefficientsPullout interaction coefficients between backfill materials and geogrid

Geogrid EfficienciesGeogrid Efficiencies

Backfill Materials

Prempramote (2005) Shehzad (2008)

EEφφ Ec EEφφ Ec

Sand only -- -- 98.19 89.12

Tire chips-sand mixture (30:70 % by

weight)

98.06 87.10 97.37 88.01

Geogrid efficiencies from pullout and direct shear tests

0

20

40

60

80

100

120

140

0 10 20 30 40 50 60 70 80

Direct shear displacement (mm)

Dir

ect

sh

ear

str

ess

(kP

a)

σ = 30 kPa σ = 30 kPa

σ = 60 kPa σ = 60 kPa

σ = 90 kPa σ = 90 kPa

σ = 120 kPa σ = 120 kPa

FEMMeasured

Direct Shear Tests SimulationsDirect Shear Tests SimulationsComparison of measured (R=0.98) and predicted (R=0.9) direct shear resistance from sand backfill using PLAXIS software

(R=0.9)(R=0.98)

0

20

40

60

80

100

120

0 10 20 30 40 50 60 70 80

Diect Shear Displacement (mm)

Dir

ect

Sh

ear

Str

ess

(kP

a)

σ = 30 kPa σ = 30 kPa

σ = 60 kPa σ = 60 kPa

σ = 90 kPa σ = 90 kPa

σ = 120 kPa σ = 120 kPa

FEMMeasured

Direct Shear Tests SimulationsDirect Shear Tests SimulationsComparison of measured (R=0.95) and predicted (R=0.9) direct shear resistance from tire chips-sand backfill using PLAXIS software

(R=0.9)(R=0.95)

PulloutPullout TestsTests SimulationsSimulations

0

20

40

60

80

100

120

0 10 20 30 40 50 60 70 80

Pullout displacement (mm)

Pu

llou

t re

sis

tan

ce

(kN

/m)

σ = 30 kPa σ = 30 kPa

σ = 60 kPa σ = 60 kPa

σ = 90 kPa σ = 90 kPa

σ = 120 kPa σ = 120 kPa

PLAXIS Measured

Comparison of measured and predicted pullout resistance from sand backfill

R=0.7

0

20

40

60

80

100

0 10 20 30 40 50 60 70 80

Pullout displacement (mm)

Pu

llou

t re

sis

tan

ce

(kN

/m)

σ = 30 kPa σ = 30 kPa

σ = 60 kPa σ = 60 kPa

σ = 90 kPa σ = 90 kPa

σ = 120 kPa σ = 120 kPa

PLAXIS Measured

PulloutPullout TestsTests SimulationsSimulationsComparison of measured and predicted pullout resistance from tire chips-sand backfill

R=0.6

0

20

40

60

80

100

120

0 10 20 30 40 50 60 70 80

Pullout displacement (mm)

Pu

llo

ut

res

ista

nc

e (

kN

/m)

σ = 30 kPa σ = 30 kPa σ = 30 kPa

σ = 60 kPa σ = 60 kPa σ = 60 kPa

σ = 90 kPa σ = 90 kPa σ = 90 kPa

σ = 120 kPa σ = 120 kPa σ = 120 kPa

FLAC (Hypoplaticity)Measured PLAXIS (MC)

PulloutPullout TestsTests Simulations Simulations ComparisonComparison

Comparison of predicted pullout resistance from PLAXIS and FLAC for sand backfill

Sensitivity AnalysesSensitivity Analyses

0

20

40

60

80

100

120

140

0 20 40 60 80Pullout displacement (mm)

Pu

llo

ut

res

ista

nc

e (

kN

/m)

σ = 30 kPa σ = 30 kPa σ = 30 kPa

σ = 60 kPa σ = 60 kPa σ = 60 kPa

σ = 90 kPa σ = 90 kPa σ = 90 kPa

σ = 120 kPa σ = 120 kPa σ = 120 kPa

Measured R = 0.7 R = 0.9

Comparison of measured and predicted pullout resistance from sand Backfill at different R values using PLAXIS software

0

20

40

60

80

100

120

0 10 20 30 40 50 60 70 80

Pullout displacement (mm)

Pu

llo

ut

res

ista

nc

e (

kN

/m)

σ = 30 kPa σ = 30 kPa σ = 30 kPa

σ = 60 kPa σ = 60 kPa σ = 60 kPa

σ = 90 kPa σ = 90 kPa σ = 90 kPa

σ = 120 kPa σ = 120 kPa σ = 120 kPa

Measured R = 0.6 R = 0.9

Sensitivity AnalysesSensitivity AnalysesComparison of measured and predicted pullout resistance from tire chips-sand backfill at different R values using PLAXIS software

0

20

40

60

80

100

120

0 10 20 30 40 50 60 70 80Pullout displacement (mm)

Pu

llo

ut

res

ista

nc

e (

kN

/m)

σ = 30 kPa σ = 30 kPa σ = 30 kPa

σ = 60 kPa σ = 60 kPa σ = 60 kPa

σ = 90 kPa σ = 90 kPa σ = 90 kPa

σ = 120 kPa σ = 120 kPa σ = 120 kPa

EA = 583 kN/m EA = 1000 kN/mMeasured

Sensitivity AnalysesSensitivity AnalysesComparison of measured and predicted pullout resistance from sand backfill at different axial stiffness values using PLAXIS software

0

20

40

60

80

100

120

0 10 20 30 40 50 60 70 80

Pullout displacement (mm)

Pu

llo

ut

res

ista

nc

e (

kN

/m)

σ = 30 kPa σ = 30 kPa σ = 30 kPa

σ = 60 kPa σ = 60 kPa σ = 60 kPa

σ = 90 kPa σ = 90 kPa σ = 90 kPa

σ = 120 kPa σ = 120 kPa σ = 120 kPa

EA = 583 kN/m EA = 1000 kN/mMeasured

Sensitivity AnalysesSensitivity AnalysesComparison of measured and predicted pullout resistance from tire chips- sand backfill at various axial stiffness values using PLAXIS software

ConclusionsConclusions

Weight of the MSE can be reduced by Weight of the MSE can be reduced by 28% using tire chips-sand mixture28% using tire chips-sand mixture

Cost of MSE structure can be reduced Cost of MSE structure can be reduced 30% by using Tire chips mixture30% by using Tire chips mixture

Efficiency of the geogrid can be Efficiency of the geogrid can be increased by improving axial stiffness increased by improving axial stiffness and interaction coefficient of the geogridand interaction coefficient of the geogrid